Method of inhibiting foam in a lubricating oil composition



United States Patent 3,024,194 METHOD OF INHIBITING FOAM IN A LUBRI- CATING OIL COMPOSITION Elliott S. Francis, Glenshaw, and Robert R. Shoemaker,

Pittsburgh, Pa., assignors to Gulf Research & Development Company, Pittsburgh, Pa., a corporation of Delaware No Drawing. Filed Mar. 19, 1958, Ser. No. 722,387 6 Claims. (Cl. 25249.6)

This invention relates to the prevention of foaming of oils and oil compositions, particularly hydrocarbon oils and synthetic oils having oil-like properties.

Oils and oil compositions such as hydrocarbon oils and synthetic oils tend to foam or froth when agitated in the presence of gases or vapors, such as air, steam, oil vapors, products of combustion, and the like. The amount of foam or froth varies with the conditions under which the oil compositions are agitated, as well as the character of the composition. Under some conditions, the volume of foam or froth produced is many times that of the original oil, and even with mild agitation, substantial amounts of foam are produced in many oil compositions. In preparing and using such oils and oil compositions commercially, they are subjected to agitation under a wide range of conditions and frequently undesirable amounts of foam or floth are produced.

Various means of combating such foaming of oils and oil compositions have been proposed. For instance, mechanical devices have been proposed for destroying or breaking foam as it is formed. Likewise, the incorporation of certain oil-soluble compounds in the oil has been proposed as a means of preventing foaming; such compounds have been referred to as anti-foam agents." Unfortunately, no agent of this type has been found which is completely satisfactory in all types of oils. While some agents have effectively reduced foaming in the heavier oils, i.e., oils having a viscosity above about 100 at 100 F., they have been less effective in light oils and synthetic oils, i.e., oils having a viscosity below about 100 at 100 F. Some of the prior anti-foam agents actually increase the amount of foam formed in light oils and synthetic oils. In some instances, the prior anti-foam agents have reduced foaming for a short period of time, their effectiveness rapidly diminishing in use. In other instances, the prior anti-foam agents have been added to the oil in such amounts that the desirable properties of the oil are impaired.

Among the objects achieved by this invention is the provision of an improved method of preventing foaming of oils and oil compositions, including light and heavy hydrocarbon oils and synthetic oils in which the normal foaming tendency of the oil is effectively abated or suppressed for long periods of use without deleteriously affecting the other properties of the oil.

Another object achieved by the present invention is the provision of new and improved anti-foam agents and compositions capable of abating and inhibiting foaming of oils and oil compositions when dispersed therein in minute amounts.

A further object achieved by the present invention is the provision of new and improved oil compositions, particularly improved light mineral oils and synthetic oils, having marked resistance to foaming and other advantageous properties including resistance to emulsification and containing minute amounts of an oil-insoluble antifoam agent finely dispersed therein.

We have discovered that the foaming of oils can be effectively suppressed or prevented without substantial modification of the desirable properties of such oils by forming in the oil a stable, fine dispersion of a small amount of an organo-silicol condensation product which has been subjected to ionizing radiation for a time sufiicient for said condensation product to absorb at least about 6 megareps. of radiation. We have found that an oil containing such an irradiated organo-silicol condensation product as a stable, finely dispersed phase is markedly resistant to foaming even under the most violent conditions encountered in commercial practice. The presence of the finely dispersed irradiated organo-silicol condensation product in the oil apparently causes the film of the oil foam to rupture, thereby quickly destroying the foam. In fact, particularly when an adequate amount of irradiated organo-silicol condensation product is used, its presence so rapidly breaks the oil foam that substantially all foam is destroyed as fast as it is formed.

We have found that an anti-foam agent comprising an organo-silicol condensation product can be converted to an improved product by subjecting the organo-silicol condensation product to ionizing radiation for a time suificient for said condensation product to absorb at least about 6 and preferably about 10 to about 1000 megareps. of radiation while removing heat therefrom at a rate sufiicient to maintain the bulk temperature of the condensation product below its decomposition or vaporization point. For example, we have found that in order to obtain a product which will materially reduce the foaming of synthetic oils, the total amount of energy absorbed by the organosilicol condensation product should be above about 6, preferably about 10 to about 1000 and more particularly about 20 to about megareps. If six or less megareps. of energy is absorbed, the irradiated product is not substantially improved with respect to its anti-foam properties for synthetic oils over the unirradiated organo-silicol condensation product. Such a six-magarep. irradiated product is only slightly effective as an anti-foam agent in mineral seal oils. If more than about 1000 megareps. of energy are indiscriminantly absorbed without removal of heat, the resulting product may be a decomposition product having little or no value as an anti-foam agent. A megarep. (Mrep.) is equal to one million reps. A rep is defined as that dose of any ionizing radiation which produces energy absorption of 83.8 ergs per gram of material.

While the total amount of energy which must be absorbed by the organo-silicol condensation product to obtain the desired product is critical, extreme care must be exercised in irradiating the organo-silicol condensation product. During irradiation the organo-silicol condensation product absorbs the high energy particles which are moving at a high rate of speed. This movement is transferred upon absorption in part into heat. If irradiation is left uncontrolled and is permitted to proceed at too great a rate, the temperature of the organo-silicol condensation product being treated can be raised to such a level that appreciable decomposition and degradation thereof takes place. Since we have found that these adverse results are produced at elevated temperatures, particularly starting at temperatures of about 260 C. for organo-silicols having viscosities above about 20 centistokes at 25 C., at no time therefore should the temperature be permitted to rise above about 260 C. with these materials. Desirably the organo-silicol condensation product being irradiated should be maintained during the irradiation period at a temperature as near the organo-silicol condensation product input temperature as possible so that the changes taking place in the organosilicol condensation product are those resulting from irradiation rather than from heat.

Heat resulting from irradiation can be removed from the organo-silicol condensation product in many ways. One method comprises subjecting the organo-silicol condensation product to ionizing radiation, removing the organo-silicol condensation product from the radiation zone as the temperature thereof rises to the levels defined above, reducing the temperature of the organosilicol condensation product to a low temperature, such as about 70 to about 150 F., by recycling to a cooling zone, recycling said cooled organo-silicol condensation product to the radiation zone, and thereafter continuing such cycle until the organo-silicol condensation product has absorbed the required amount of energy. Another method, though not preferred, because of the poor heat conductivity of organo-silicol condensation product, resides in the use of cooling coils immersed in the organosilicol condensation product being irradiated to remove the heat therefrom.

The time required for irradiation is extremely important from an economic point of view. When the process is carried out over an extended period of time, it becomes unattractive for commercial use. At the same time, irradiating the organo-silicol condensation product in too short a time makes it extremely difiicult to control the reaction and to maintain the organo-silicol condensation product within the desired temperature limits. We have found, for example, that an irradiation period per gram of material being irradiated of about 0.1 to about 20 seconds is sufiicient to effect the desired result if we use a 2 million volt Van de Graatf accelerator producing an electron beam at an output of 500 watts. With other power sources, of course, the time will be changed in accordance with the power of the source. Provided heat is removed at a rate sufiicient to prevent substantial decomposition or vaporization of the organosilicol condensation product, any irradiation rate can be employed, through extremely high rates may involve technical difliculties.

We do not wish to limit this invention to any particular method of radiation inasmuch as the effects of radiation on organo-silicol condensation products are essentially the same insofar as anti-foam characteristics are concerned regardless of the radiation source. Ionizing radiations can be obtained, for example, using radio isotopes, nuclear reactors or high energy particle accelerators. Examples of radio isotopes which can be used are cobalt 60 for gamma and strontium 90 for beta. Operating nuclear reactors of intermediate or full power size can be used as a source for either gamma rays or neutrons or both. Particle accelerators such as the cyclotron, bevatron, synchrotron, Van de Graaif, or X-ray machines can also be used.

In efiecting irradiation of the organo-silicol condensation product, the condensation product can be introduced into a well in a nuclear reactor or through a tube which traverses the reactor. In some instances where it is desirable to expose the condensation product to fast or high energy neutrons only, and in the substantial absence of beta and gamma radiation, the irradiation can be conducted outside of the reactor using a collimated beam of fast neutrons. Such a collimated beam of fast neutrons can be obtained, for example, as described in U.S. Patent No. 2,708,656 to Enrico Fermi and Leo Szilard, by inserting a hollow shaft or tube into the central portion of the reactor. Gamma rays can be screened from the fast neutron beam by means of a sheet of bismuth metal extending across the path of the beam.

A neutron-free radiation source can be obtained directly from a homogeneous reactor by separating the radioactive fission gases, xenon and krypton, from the reactor core by conventional or modified gas-liquid separating means. A continuous supply of the radioactive fission gases could be obtained from such a reactor. The fission gases have a very high intensity of beta and gamma radiation but a very short half life. These gases possess about one percent of the total fission energy. The gases are chemically inert and therefore would not form undesired side reaction products.

While we are not certain as to the exact nature of the changes which take place when an organosilicol condensation product is subjected to ionizing radiation, we believe that extensive cross linking occurs. The organosilicol condensation products change from a medium viscosity liquid, for example, about 3700 SUS at F., to a very viscous liquid and finally to a soft solid as the irradiation dose increases from 6 up to about 100 megareps. The solubility of the organo-silicol condensation product in ordinary solvents decreases while the melting point increases as the irradiation dose increases. Thus, some polymers which are initially soluble in solvents are not soluble after being irradiated. An eflfective method of separating the irradiated products from unconverted products or those which are less irradiated thus comprises washing the irradiated mass with a solvent such as hexane, benzene, or the like. The unconverted or less irradiated organo-silicol condensation product is dissolved by the solvent and can be separated from the irradiated product by filtration. The residue remaining on the filter comprises the irradiated organo-silicol condensation product. While we can use the entire irradiated mass without separating the unconverted or perhaps less irradiated organo-silicol condensation product for the purpose of our invention, we prefer to use only the material which has absorbed the full dose of radiation. The unconverted organo-silicol condensation product, in some instances, particularly in light oils including mineral seal oil and synthetic oils, gives rise to foam formation. Therefore, if the unconverted organo-silicol condensation product is not separated from the irradiated organo-silicol condensation product, the efiiciency of the irradiated material as an anti-foam agent in oils, particularly synthetic oils, is materially reduced.

In the practice of this invention, various irradiated oil-insoluble liquid organo-silicol condensation products having a surface tension lower than that of the oil and capable of being stably and finely dispersed in the oil may be employed as anti-foam agents.

The organo-silicol condensation products which are subjected to irradiation prior to their use as anti-foam agents according to this invention are composed primarily of a plurality of silcion atoms linked together through oxygen atoms, each silicon atom having attached to it at least one organic radical either directly or through an oxygen atom, and they may contain one or more other substituents, such as hydroxyl groups or halides. Typical organo-silicol condensation products which have been found suitable for the purposes of our invention include for example the liquid organo-siloxanes.

The organo-siloxanes are sometimes referred to as the organo-silicone polymers or condensation products as a result of the fact that they are principally composed of organo-silicone residues. They vary in composition depending upon the materials from which they are produced and the method of production. They are usually produced as condensation or polymerization products of the organo-silicols including the mono-silicols, di-silicols and tri-silicols and mixtures of these silicols. The organosilicone residues from these three silicols are of three different types. The silicone residue of the mono-silicols may be represented generically by the formula R- i1 o in which R, R or R" represent similar or dissimilar organic radicals such as alkyl, aryl, aralkyl, alkaryl or heterocyclic groups. The silicone residue of the disilicols may be represented generically by the formula -SiO- in which R and R represent similar or dissimilar orgame radicals such as alkyl, aryl, aralkyl, alkaryl or heterocyclic groups. The silicone residue of the trisilicols may be represented by the formula in which R represents an organic radical such as an alkyl, aryl, aralkyl, alkaryl or heterocyclic group.

The organo-siloxanes or organo-silicone condensation products may contain any one or all three of the above types of silicone residues depending upon whether they are produced from pure silicols or mixtures of two or three of the mono-, diand tri-silicols. The condensation products obtainable may be straight chain, cyclic or cross polymerization products and include both solids and liquids.

The organo-mono-silicols when polymerized alone can form only the dimer having the generic formula in which R, R and R represent similar or dissimilar organic radicals such as alkyl, aryl, alkaryl, aralkyl and heterocyclic groups. These compounds are generally liquid.

The organo-di-silic0l compounds when polymerized alone tend to produce predominantly straight chain polymerization products which may be generically represented by the following formula:

wherein R represents an organic radical, such as alkyl, aryl, aralkyl, alkaryl or heterocyclic group, R is a similar or dissimilar organic radical and it may be one or higher depending upon the number of organo-silicon oxide residues in the complex molecule resulting from the condensation and dehydration of the organo-silane diol.

When the organo-silane diols are polymerized in the presence of an organo-silane-rnonol the monol tends to substitute at the end of the chain in place of at least one hydroxyl group and produce compounds having the in which R, R and R" represent similar or dissimilar organic radicals such as the alkyl, aryl, aralkyl, alkaryl or heterocyclic group, X may be such an organic radical or a hydroxyl group and n may be one or higher. Similarly other terminal groups may be substituted in these compounds in which case the generic structural formula may be represented by in which R and R represent similar or dissimilar organic radicals as above and X and Y represent similar or dissimilar organic radicals or inorganic substituents such as hydroxyl radicals, halides or the like and n may be one or higher.

The condensation products obtained from pure organosilane triols are generally resinous solids because of the extensive cross polymerization which takes place. However, liquid condensation products suitable for irradiation and subsequent use for the purposes of our invention may be obtained from mixtures of tri-silicols with mono-: or di-silicols or both. In such mixtures cross polymerization is more limited and there may be obtained suitable oil insoluble liquid condensation products containing for example cross polymerization products having a formula of the following type:

in which R, R and R" may be similar or dissimilar alkyl, aryl, aralkyl, alkaryl or heterocyclic groups and n may be one or more. It will be understood that this formula is merely illustrative of cross polymerization products and that the products may take other forms in which two or more cross linkings between polymers are established. Such compounds may take a form in which they resemble cyclic compounds for example:

in which R, R and R" may be similar or dissimilar alkyl, aryl, aralkyl, alkaryl or heterocyclic groups.

The molecular weight and other properties of the organo-siloxanes or silicone condensation products vary with the extent of the dehydration and condensation of the silicols from which they are produced and with the particular organic radicals present. While some of them are resinous or rubbery solids, others are oily liquids. For the purposes of the present invention, the liquid condensation products are preferred. In general, we find the condensation products containing simple organic radicals, such as methyl, ethyl and short-chain alkyl groups, most advantageous for the purposes of our invention.

For example, we have found that the irradiated condensation products of the methyl silicols are, in general, good anti-foam agents. The irradiated condensation products of di-methyl-silane diol are most advantageous for this purpose. However, irradiated condensation prod. ucts of mixtures containing trimethyl-silane monol, dimethyl-silane diol and methyl-silane triol can also be used. Dimethyl-silane diol has the following formula:

Cl C II;

dirnethyl silanediol In this reaction all of the silicon tetrachloride may not be converted to the di-methyl-silane diol. The product may then consist of a mixture of trimethyl-silane monol, di-methyl-silane diol and methyl-silane triol. This reaction product may be polymerized directly and the polymerized product then subjected to irradiation to produce satisfactory anti-foam agents for the purpose of our invention. Alternatively, intermediate separation may be efiected so that polymers of the individual silicols may be produced, the individual polymers thereafter being irradiated.

For the purpose of describing our invention in more detail hereinafter reference will be made particularly to the class of organo-silicol condensation products designated as polydimethyl siloxanes represented by the structural formula wherein n is an integer of at least one. These polydimethyl siloxanes depending upon the extent of the polymerization vary in viscosity upwardly from about 0.65 centisoke at 25 C. to about a million centistokes. Dow- Corning Fluid 200 marketed by Dow-Corning Corporation in the viscosity range of about 100 to about 1000 centistokes at 25 C. has been irradiated and thereafter utilized successfully to reduce the foaming of oils as will be illustrated more fully hereinbelow. It is to be understood that this invention is not limited to the use of irradiated polydimethyl siloxanes as anti-foam agents, but contemplates other irradiated organosilicol condensation products which are substantially insoluble in oils and have surface tensions lower than the surface tensions of the oils.

As a class, the irradiated condensation products are for all practical purposes substantially oil-insoluble. They are also substantially insoluble in Water and aqueous solutions. On the other hand, they can be readily dispersed in hydrocarbon and synthetic oils to form stable dispersions containing extremely fine particles of irradiated products. In fact, we have prepared oil compositions containing such irradiated condensation products dispersed therein, in which the majority of the dispersed particles range from 2.0 to 0.3 micron in diameter or less. Such fine dispersions of these irradiated condensation products in oils are very stable and are markedly resistant to foaming. Some oil compositions containing from to 100 parts per million of these compounds finely dispersed therein yield little or no foam when subjected to drastic foaming tests. In fact, some compositions containing as low as 0.05 part per million of a dispersed irradiated siloxane condensation product show a measurable resistance to foaming. The light oils and synthetic oils generally require from about 0.00001 to 1 percent by weight to effectively reduce foaming.

The irradiated condensation products of the methylsilicols described above are merely illustrative of this type of anti-foam agent. The irradiated condensation products of other organo-silicols are also effective in suppressing foaming of hydrocarbon oils and may be employed as the anti-foam agent. The amount used should be sufficiently in excess of the solubility of the compounds in the oil to give the required amount of dispersed phase necessary to prevent foaming under service conditions. For this reason, the irradiated siloxanes which are substantially oil-insoluble are most advantageous. While the compounds containing the simple organic radicals, such as methyl, ethyl and short-chain alkyl groups, are especially advantageous for the present purposes, satisfactory results can also be obtained with irradiated organo-siloxanes containing other organic radicals, such for example as irradiated aryl siloxanes, irradiated alkaryl siloxanes and irradiated substituted aryl siloxanes.

The particle size of the irradiated condensation product dispersed in the hydrocarbon oil has a marked effect upon the resistance to foaming so imparted to the oil compositions. In general, oil compositions containing dispersions of the irradiated condensation product in which the particles are about 2.0 microns and less in diameter are particularly advantageous for the present purposes. Such oil compositions are very stable in storage and under service conditions, and they have a high resistance to foaming which they retain over long periods of use.

Since good resistance to foaming can be readily obtained with exceedingly small proportions of our new antifoam agents finely dispersed in the oil, the anti-foam agents of our invention do not deleteriously modify the other properties of such compositions. Accordingly, the desired foam-resisting properties can be imparted to such oils Without impairing their effectiveness as lubricants or for other intended uses.

In the commercial practice of this invention, oil compositions may be produced directly in which the antifoam agent is present in the desired small amount and fine dispersion. However, in certain embodiments of the invention, oil compositions initially containing relatively coarse dispersions and relatively high concentrations of the anti-foam agent may be first prepared and the desired finely dispersed agent concentration may be produced in the oil during use by agitation thereof in the lubricating system, such as by gear pumps and other mechanisms. Such production of the desired fine dispersions in situ in the oil during use is sometimes advantageous. Of course, the amount of anti-foam agent and the fineness of the dispersion necessary to prevent foaming in a given case vary somewhat with the particular oil and agent employed as well as the service conditions to which the oil composition is subjected.

In preparing our improved oil compositions, the antifoam agent may be incorporated in the oil or oil composition by any suitable method capable of producing a stable fine dispersion of the agent in the oil. For example, where the anti-foam agent is to be added to a heavy mineral oil, it may first be incorporated in a light hydrocarbon or other suitable carrier, such as mineral seal oil, gasoline, naphtha, hexane and benzene, and this anti-foam composition may then be introduced into the oil to which it is desired to give anti-foam properties. After such an anti-foam composition has been formed it may be incorporated in the oil or oil composition simply by mixing and agitating the solution therewith. A fine dispersion of the anti-foam agent in the oil is thus ob tained. A convenient anti-foam concentrate for such use would contain 1.0 percent of active anti-foam agent. To add 0.001 percent anti-foam agent to the final oil would require the addition of 0.1 percent of the anti-foam concentrate. Where it is desired to form directly a dispersion of the anti-foam agent in the oil, various commercial colloid mills may be employed to disperse finely the agent in the oil. Also, gear pumps may be employed to disperse the anti-foam agent in the oil. The use of such gear pumps is advantageous in many embodiments of this invention, particularly those wherein fine dispersions of the anti-foam agents are produced in situ in the oil. In some instances, the organo-silicol condensation product can be added to the oil and then the entire mixture subjected to ionizing radiation. Where such technique is employed, the vehicle should be one that is relatively insensitive to radiation under the conditions employed. Other methods and apparatus may also be employed in dispersing these irradiated agents in oils or oil compositions.

It is sometimes advantageous to first disperse the liquid anti-foam agent in part of the oil and then add this concentrate dispersion to the remainder of the oil. Such concentrate dispersions can be readily prepared as stable uniform compositions. For instance, a mixture of oil and anti-foam agent in the desired proportions may be continuously circulated through a gear pump until a stable concentrate containing a uniform dispersion of the agent is obtained. Thus, standardized concentrates can be prepared which can be added to lubricating compositions as needed. In such case, the desired amount of concentrate is added to the oil composition and the mixture is agitated until uniform.

Also, such concentrates are themselves valuable antifoam compositions. As they contain a preformed, dispersed, insoluble liquid phase of the desired particle size,

they quickly break oil foams, as well as suppress foaming in general. For instance, when added to oil or oil compositions which have foamed, they rapidly destroy the foam present and stop further foaming. In such cases, they can be quickly blended with oils, oil compositions and crude oil and uniformly incorporated therein before serious foaming occurs.

For such purposes, oil concentrates containing from 0.1 to percent by weight and more of finely dispersed anti-foam agent are advantageous. By adding from 0.01 to 10 percent by weight of such concentrates to mineral lubricating oils, improved lubricants having marked resistance to foaming are readily and easily obtained.

The anti-foam agent of the invention is effective in suppressing and preventing foaming in oils and oil compositions generally including mineral oils and fatty oils such as vegetable and animal oils and fatty oil compositions. The anti-foam agent of the invention is, however, particularly advantageous in connection with light hydrocarbon oils, i.e., mineral seal oil, naphtha, kerosene and the like, and synthetic oils by which is meant substances having oil-like properties and synthetically produced from various chemical compounds by condensation, polymerization, hydrogenation, or other such processes.

One advantageous field of use for the anti-foam agents of our invention is in lubricants for internal combustion engines, such as automotive, aviation, diesel and like engines, because We have found that even under the high temperature of operation of these engines, these antifoam agents retain their foam-inhibiting properties. In lubricating such engines, appreciable foaming of the motor oil seriously interferes with elfective lubrication. For instance, aviation oils (either straight or compounded oils) tend to foam at the low barometric pressures encountered at high altitudes. Also in lubricating such engines, particularly aviation engines, the lubricating oil is circulated under pressure through the parts to be lubricated. In doing so gear pumps are usually employed in supplying pressure oil to the engine and returning the oil from the engine sumps to the reservoir tank. In such systems, the scavenger pump is usually of such capacity as to maintain the engine sump in a substantially dry condition. With such dry sump systems, the scavenger pump frequently pumps large volumes of air with the oil, this air becoming dispersed in the oil. Under such conditions, excessive foam often leads to loss of the oil from the engines and impairs the lubrication. By the present invention, such foaming can be readily overcome or suppressed. For example, an appropriate amount of our anti-foam agent can be introduced into the circulating oil and dispersed therein by the gear pumps, or a concentration of the anti-foam agent can be intermittently injected into the oil and uniformly dispersed therein by such gear pumps Whenever substantial amounts of foam appear in the system. Further, such foaming can be prevented and the engine effectively lubricated at all times by employing an improved lubricant containing these antifoam agents dispersed therein from the beginning.

Our anti-foam agents, concentrates and improved motor oils are also useful and advantageous in lubricating certain types of engines using splash lubrication. Modern diesel engine oils and heavy duty motor oils usually contain relatively large amounts of additives of the detergent or detergent-dispersion type. These additives include materials such as the oil-soluble salts of metallic or organic bases with various detergent-forming acids. The metallic bases include the alkali metals, Cu, Mg, Ca, Sr, Ba, and the like. The organic bases include primary, secondary, tertiary, and quaternary amines. The detergent-forming acids incldue fatty acids containing as high as thirty carbon atoms, wool fat acids, petroleum sulfonic acids, sulfuric acid mono-esters, phosphoric acid monoand di-esters, etc. Many of these detergents promote foaming and produce detergent-containing lubricating '10 oils which foam badly. By the present invention foaming caused by the addition of detergents to such oils is efiectively suppressed and improved non-foaming oils are readily obtained.

Still another field of use for the anti-foam agents of our invention is in the light oils used in steam turbines. With these light oils, agitation may produce considerable foaming. By the present invention, such foaming of light oils is effectively prevented. Furthermore, there is often a tendency for steam turbine oils to emulsify with the water with which they are mixed. We have found that the anti-foam agents of our invention do not deleteriously affect the emulsification characteristics of such oils.

A particularly advantageous field of use for the antifoam agents of our invention is in synthetic lubricants which are subjected to severe agitation under mild or moderately cool operating temperatures. Examples of such lubricants are organic esters including di-2-ethyl hexyl sebacate, dioctyl phthalate and dioctyl azelate; polymerized olefins; co-polymers of alkylene glycols and alkylene oxides; polyalkyl silicone polymers such as methyl phenyl silicone; and the like.

Our anti-foam agents and concentrates are useful in any oil or oil composition whether used as a lubricant or not, and in which it is desired to prevent foaming. They are particularly effective, however, in combating foaming in mineral oils and synthetic materials having oil-like properties.

The lubricating oils of our invention can contain detergents, as mentioned above, and/or other additive agents including oiliness and extreme pressure agents, such as aromatic chlorine compounds, stabilized chlorinated parafiins, sulfurized fatty oils, and high molecular weight ketones and esters; viscosity index improvers, such as the high molecular weight polymers of isobutylene and the polymers of methacrylic esters; pour point depressants, such as a condensation product of'chlorinated wax and naphthalene and a condensation product of chlorinated wax and phenol followed by further condensation of this reaction product with organic acids; an anti-rust agent such as cocoamine isoamyl octyl orthophosphate; and corrosion and oxidation inhibitors, such as 2,6-di-tertiary butyl-4-methyl phenol, tri-phenyl phosphite, tributyl phosphite, beta naphthol, and phenyl betanaphthylamine. Many of these agents tend to promote foaming and we have found that an anti-foam product of our invention will suppress the foaming caused by the addition of such agents to an oil without deleteriously affecting the beneficial characteristics given to the oil by these additives.

The effectiveness of an organo-silicol condensation product which has been subjected to ionizing radiation according to our invention in preventing foaming in different oils and oil compositions may be demonstrated by means of ASTM Test Designation D892-46T in which the oil or oil composition is controllably aerated under fixed conditions so that the results obtained in a series of tests are directly comparable.

The polydimethyl siloxane which was subjected to ionizing radiation for purposes of illustrating the invention was that marketed by Dow-Corning Corporation as Dow-Corning Fluid 200 having a viscosity of about 1015 centistokes at. 77 F. The polydimethyl siloxane was enclosed in a polyethylene bag and irradiated to various dosages in a Van de Graaif accelerator. The bulk temperature of the polydimethyl siloxane was maintained between about and 200 F. during irradiation. The total energy absorption is shown in connection with the various specific examples.

In preparing samples of oil for the foam test, various procedures for adding the anti-foam agent were employed. In some instances, the agent was added directly to the oil. In other instances a concentrate was prepared using as the base either benzene or an oil of the same type being tested. When a concentrate was prepared, the anti-foam agent was thoroughly dispersed in 11 the base by circulating the mixture for eight hours through a gear pump. All finished blends were obtained by mixing the anti-foam agent or concentrate thereof with the oil to be tested in a Waring blendor for at least five minutes. The particular procedure employed is designated by the foot notes accompanying the tables.

The data summarized in Table I will illustrate the advantageous results obtained by incorporating in an SAE 50 mineral lubricating oil a polydimethyl siloxane which had been subjected to a total energy absorption of 100 megareps. The entire irradiation product was used.

The mineral lubricating oil used in preparing the compositions illustrated in Table I was a highly refined paraffinic mineral lubricating oil of SAE 50 grade having an API gravity of 27.9, a viscosity of 1169 at 100 F. and 100 at 210 F., a viscosity index of 101, a flash point (DC) of 570 F., a fire point (DC) of 625 F. and a pour point of F. The polydimethyl siloxane which was subjected to radiation had an API gravity of 13.2, a viscosity of 3696 at 100 F. and 1532 at 210 F., a flash point (DC) of 650 F. and a pour point below 50 F.

Table l Composition A B C D E Percent by weight Base oii-27.9 API-1169 SUS at 100 F 100 99.9 99.99 99.999 99.9999 Poiydirncthyl siloxane (100 mrep. irradiated) 1 0.10 2 0.010 2 0. 001 2 0. 0001 Foam test (ASTM D892-46T):

Foaming tendency, m1. at

5 min. at

75 F..-- 420 150 0 0 70 200 F..- 130 70 10 0 85 75 F. after test at 200 F 240 85 o o 30 1 Added from a 1% mineral oil concentrate. I Obtained by further dilution of Composition B with the base oil.

As shown by the data summarized in Table I, the SAE 50 grade oil containing 0.0001 to 0.1 percent by weight of irradiated polydimethyl siloxane is substantially improved in its anti-foam characteristics.

The data summarized in Table II will illustrate the advantageous anti-foam characteristics imparted to a synthetic lubricating oil by incorporating therein a small amount of polydimethyl siloxane which had been subjected to a total energy absorption of 100 megareps. The total irradiation product was used. The synthetic lubricating oil was a mixture composed of 66% parts of methyl phenyl silicone and 33 /3 parts of di-Z-ethylhexyl sebacate.

Table II Composition, percent by weight F G H I Synthetic oil by volume methyl phenyl silicone and M by volume di-2- ethylhexyl sebacate) 100 99.9 99. 99 99.999 Polydimethyl siloxane (100 mrep.

irradiate l 0.10 3 0. 01 3 0.001 Foam test (ASTM D892-46T):

Foaming tendency, ml. at 5 min.

75 F 450 180 425 200 F 425 110 80 265 75 F. after test at 200 F 465 25 185 420 1 added from a 1% synthetic oil concentrate. 1 Obtained by further dilution oi composition G with the synthetic oil As shown by the data summarized in Table 11, the synthetic oil containing 0.01 to 0.1 percent by weight of irradiated polydimethyl siloxane is substantially improved in its anti-foam characteristics. While some improvement is obtained with 0.001 percent, particularly at 200 F., the improvement is not as great as that obtained using a larger amount of the irradiated product.

The data summarized in Tables III and IV will illustrate the advantageous anti-foam characteristics imparted to a synthetic lubricating oil and mineral seal oil, respectively, by incorporating in these oils 0.01 percent by weight of an irradiated polydimethyl siloxane. A comparison is also made between an oil containing irradiated and unirradiated polydimethyl siloxane. The importance of utilizing a polydimethyl siloxane which has been subjected to ionizing radiation for a time suflicient to absorb above about 6 megareps. of radiation is also illustrated. In preparing the compositions shown in Tables III and IV the total irradiation product Was employed. The mineral seal oil employed had the following typical characteristics.

Gravity, API Flash point, 0C, F. Fire point, 0C, F. Pour point, F. Distillation (gas oil):

Over point, F. 50% point, F. End point, F.

Table III Composition, percent K L by weight Synthetic oil by volume phenyl silicone and by volume di-2ethylhexyl sebacate)- Polydimethyl siloxane (unirradiated) Polydimethyl siloxane, mrep. irradiated:

Foam test (ASTM Foaming tendency, ml. at 6 min. at-

1 Added from a 3% mineral oil concentrate. 2 Added from a 1% concentrate in benzene. 9 Added from a 1% synthetic oil concentrate.

Table l V Composition, pen R S cent by weight Mineral seal oil 41.7 API Polydimethyl siloxane (unirradiate Polydimethyl siloxane, mrep. irradiated- Foam test (ASTM Foaming tend- I Added from a 3% mineral oil concentrate. 3 Added directly. 8 Added from a 1% mineral oil concentrate.

The data in Table III shows that the addition of unirradiated polydimethyl siloxane and the same polydimethyl siloxane irradiated to 6 megareps. increases the foaming tendency of a synthetic oil when tested at 200 F. and at 75 F. following the 200 F. test. The addition of polydimethyl siloxanes which have been subjected to higher doses of radiation decreases the foaming tendency of the synthetic oil. The data in Table IV shows that some improvement in the foaming characteristics of mineral seal oil can be obtained with polydimethyl siloxane irradiated to 6 megareps. and that such an irradiated polydimethyl siloxane is more eifective than unirradiated polydimethyl siloxane in two out of the three tests. Substantial foam reduction, however, requires the addition of a polydimethyl siloxane irradiated above about 6 megareps.

The properties of an improved composition of the invention containing 0.01 percent by weight of irradiated polydimethyl siloxane were substantially the same as those of the base oil as shown by the inspection data in the following table.

While our invention has been described above with reference to various specific examples and embodiments, it will be understood that the invention is not limited to such illustrative examples and embodiments, and may be variously practiced within the scope of the claims hereinafter made.

We claim:

1. A process of suppressing foaming in an oil having foaming tendencies, said oil being selected from the group consisting of mineral oils and synthetic lubricants having oil-like properties selected from the group consisting of organic esters, polymerized olefins, copolymers of alkylene glycols and alkylene oxides and polyorgano silicone polymers, said process comprising dispersing in said oil a small amount, sufiicient to improve said foaming tendencies, of an organo-silicol condensation product which has been subjected to ionizing radiation for a time suflicient for said condensation product to absorb about 6 to about 1,000 megareps. of radiation while maintaining the bulk temperature of the condensation product below its decomposition temperature, said organo-silicol condensation product being selected from the group consisting of alkyl, aryl, aralkyl, alkaryl and heterocyclic siloxanes.

2. A process of suppressing foaming in an oil selected from the group consisting of mineral oils and synthetic lubricants having oil-like properties selected from the group consisting of organic esters, polymerized olefins,

copolymers of alkylene glycols and alkylene oxides and polyorgano silicone polymers, said process comprising dispersing in said oil about 0.00001 to about 1.0 percent by weight of a dialkyl siloxane which has been subjected to ionizing radiation for a timesufficient for said dialkyl siloxane to absorb about 6 to about 1,000 megareps. of radiation While maintaining the bulk temperature of the dialkyl siloxane below its decomposition temperature.

3. A process of suppressing foaming in a hydrocarbon oil comprising dispersing in said oil about 0.00001 to about 1.0 percent by weight of a polydimethyl siloxane which has been subjected to ionizing radiation for a time sufficient for said polydimethyl siloxane to absorb about 6 to about 1,000 megareps. of radiation while maintaining the bulk temperature of the polydimethyl siloxane below its decomposition temperature, the dispersion in said oil having been formed by dispersing a mixture of said polydimethyl siloxane in a hydrocarbon oil, said mixture containing about 0.1 to about 10 percent by weight of said polydimethyl siloxane.

4. The process of claim 3 in which the hydrocarbon oil is mineral seal oil.

5. A process of suppressing foaming in a synthetic lubricant having oil-like properties selected from the group consisting of organic esters, polymerized olefins, copolymers, of alkylene glycols and alkylene oxides and polyorgano silicone polymers, said process comprising dispersing in said lubricant about 0.00001 to about 1.0 percent by Weight of the polydimethyl siloxane which has been subjected to ionizing radiation for a time suflicient for said polydimethyl siloxane to absorb about 10 to about 1,000 megareps. of radiation while maintaining the bulk temperature of the polydimethyl siloxane below its decomposition temperature, the dispersion in said lubricant having been formed by dispersing a mixture of said polydimethyl siloxane in a synthetic lubricant, said mixture containing about 0.1 to about 10 percent by weight of said polydimethyl siloxane.

6. The process of claim 5 in which the synthetic lubricant is a mixture of methyl phenyl silicone and di-2-ethylhexyl sebacate.

References Cited in the file of this patent UNITED STATES PATENTS 2,375,007 Larsen et al. May 1, 1945 2,416,504 Trautman et al Feb. 25, 1947 2,632,736 Currie Mar. 24, 1953 2,702,793 Smith Feb. 22, 1955 2,766,220 Kantor Oct. 9, 1956 2,904,481 Lawton et al Sept. 15, 1959 OTHER REFERENCES Charlesby: Effect of Molecular Weight on the Cross- Linking of Siloxanes by High-Energy Radiation, Nature, vol. 173, Apr. 10, 1954, pp. 679-680. 

1. A PROCESS OF SUPPRESSING FOAMING IN AN OIL HAVING FOAMING TENDENCIES, SAID OIL BEING SELECTED FROM THE GROUP CONSISTING OF MINERAL OILS AND SYNTHETIC LUBRICANTS HAVING OIL-LIKE PROPERTIES SELECTED FROM THE GROUP CONSISTING OF ORGANIC ESTERS, POLYMERIZED OLEFINS, COPOLYMERS OF ALKYLENE GLYCOLS AND ALKYLENE OXIDES AND POLYORGANO SILICONE POLYMERS, SAID PROCESS COMPRISING DISPERSING IN SAID OIL A SMALL AMOUNT, SUFFICIENT TO IMPROVE SAID FOAMING TENDENCIES OF AN ORGANO-SILICL CONDENSATION PRODUCT WHICH HAS BEEN SUBJECTED TO IONIZING RADIATION FOR A TIME SUFFICIENT FOR SAID CONDENSATION PRODUCT TO ABSORB ABOUT 6 TO ABOUT 1,000 MEGAREPS. OF RADIATION WHILE MAINTAINING THE BULK TEM PERATURE OF THE CONDENSATION PRODUCT BELOW ITS DECOMPOSITION TEMPERATURE, SAID ORGAN-SILICOL CONDENSATION PRODUCT BEING SELECTED FROM THE GROUP CONSISTING OF ALKYL ARYL, ARALKYL, ALKARYL AND HETEROCYCLIC SILOXANES. 